This invention relates to the preparation of chlorohydrins. More particularly, this invention relates to the preparation of chlorohydrins by hypochlorination of alpha-olefins. The chlorohydrins are useful as intermediates in the preparation of epoxides.
Conventional hypochlorination technology involves the reaction of chlorine with an alpha-olefin in water to yield the corresponding chlorohydrin. This reaction results in the formation of an excess oil phase due to the incompatibility of olefin with water or due to the formation of water-insoluble by-products. This oil phase is thought to serve as a locus for the production of undesired by-products such as dichlorides and ethers. To compensate for the incompatibility of olefin or by-products with water and reduce the formation of excess oil, large amounts of water relative to the olefin and intense mechanical mixing are used. This practice, however, causes in the subsequent dehydrochlorination of the chlorohydrin, the formation of significant volume of aqueous effluents containing organic impurities, the purification of which requires expensive treatments.
U.S. Pat. No. 5,146,011 describes a process for preparing chlorohydrins by reacting a concentrated, aqueous solution of hypochlorous acid with an unsaturated organic compound having from 2 to about 10 carbon atoms and selected from the group consisting of substituted and unsubstituted olefins and cyclic olefins. The process is optionally carried out in the presence of a surfactant such as nonylphenol ethoxylate, alkyldimethylbenzylammonium chloride and sodium dodecylbenzenesulfate, all of which contain an aromatic ring. It is known that any surfactant which contains an aromatic ring is subject to rapid oxidative reaction with chlorine or HOCl in the reaction mixture. The reaction is at temperatures from the freezing point of water up to 55.degree. C. The low reaction temperature requires use of heat exchange equipment to remove the heat of reaction. The process requires the use of high concentration (greater than 10 weight percent, preferably from 20 to 65, most preferabl y from 35 to 55 percent by weight) HOCl solutions.
British Patent Application 2 029 821 A describes a process for preparing glycerol dichlorohydrins by reacting chlorine and an emulsion of allyl chloride in water. The process requires the preparation of an emulsion of allyl chloride in water using a static mixer prior to feeding the emulsion to the reactor. To facilitate the formation of the allyl chloride-water emulsion, an emulsifier, such as a non-ionic or anionic emulsifier, is added to the allyl chloride-water mixture. In this process the reaction between the allyl chloride-water emulsion and chlorine takes place in the oily phase which produces undesirable by-products.
It would be desirable to provide a process for preparing chlorohydrins which do not have the disadvantages of the known processes described above.